Yes, so essentially what happens, when you're in the Comic section, it will automatically download the first stuff that you're reading. So the last thing you've been reading will be shown at the top of the list. You can intuitively understand it as whatever is in my list that's what's being downloaded or cached. It's not like you tag things as "offline", you just do it by reading it. And you can move things from the queue as well.
What we want is, that if you're reading offline, you should never have to plan. It's more like when you read at home and then you leave and you take it with you on your Nintendo Switch, it already has all the content. So you have, you know, your eight hours of content that you need or whatever. Of course you can't search for new stuff while you're offline. But you can at least read all the things you've been interested in so far.